I am looking at buying one for my girlfriend's birthday present but I cannot find a 16g Wifi + 3g AT&T Refurbished 2nd Gen. Does the Micro sim card tray that seems to be on the refurbished models work with both AT/T and any other micro sim card ? Wether it'd be GSM or CDMA ? I am asking because she will come and study in Canada and I have heard the CDMA networks here are not compatible with the US ones. Any help would be greatly appreciated. I have been looking thru google but can't find a definitive answer.